The invention relates to an apparatus and method for holding a thread end left in a needle of a sewing machine after completion of a sewing operation.
At the end of many sewing operations, in particular sewing a buttonhole in a fabric with a conventional automatic sewing machine, a few inches of thread end are pulled from the needle. In industrial-type sewing where operations must be repeated at maximum efficiency, this thread end frequently is sewn into the next buttonhole to leave a long and unsightly thread dangling from that button.
Several devices have been developed and used in the past in order to prevent this thread end from being left dangling. One technique is to provide a trimmer for cutting the thread end at the end of the operation. This, however, involves an additional step by the operator and an additional piece of equipment. Another approach is to use a mechanical wiper to automatically knock the thread to the side after the completion of each operation. So long as the thread end is held away from the needle the thread will simply double in the next operation and will not dangle from the sewn buttonhole. Such wipers, however, have never worked satisfactorily.
Yet another technique which has been proposed is to knock the thread end to the side by the use of a burst of air from a blower. This technique likewise has not been completely satisfactory.
The present invention relates to a unique apparatus and method in which beween sewing operations, the thread end is drawn into a tube adjacent the needle of the sewing machine by air flow into that tube. The thread end is thus held away from the needle and will simply be doubled in the next sewing operation. Providing air flow only between operations minimizes the use of supply air.
In a preferred embodiment of the invention, the air flow into the tube adjacent the needle is caused by transfer of momentum from a stream of supply air at a pressure above atmospheric pressure to air flowing through an aspirator having a passage coupled to the tube. A normally opened or normally closed valve is operated by a part of the sewing machine, for example, one of the levers, to enable the flow of air to the aspirator only between operations of the sewing machine. The tube is preferably attached at one end thereof to a foot of the sewing machine and at its other end to the aspirator mounted on the machine by a bracket or the like.
Many other objects and purposes of the invention will be clear from the following detailed descriptions of the drawings.